robotic gripper clamp needed

I need to implement a robotic gripper design for my project. I would like one that functions more like a clamping mechanism in which the
upper and lower "fingers" move toward each other in a linear direction as opposed to gripper fingers that rotate inward in a circular manner. I need it to open at least 3 inches, and it needs to be not very expensive since I need three of these grippers. Does such a product exist? If not, I'll need to design my own and would need to know what kind of actuator to use: rack and pinion, screwdriver, or linear stepper motor?
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snipped-for-privacy@keenebroadband.com wrote:

You might get to design your own. Here's the best I could find in the "cheap" category. http://www.lynxmotion.com/Product.aspx?productID&CategoryID5 http://www.budgetrobotics.com/shop/?shop=1&cartF6428&cat5&noCookiePassThrough=Y&
Gordon McComb's "Robot Builder's Bonanza" has some sketches of gripper designs that may help.
- Daniel
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I owe one of each of those. Neither opens 3". Lynxmotion is less than 2" as I recall, and Budgets is about 2-1/4, just wide enough to get around a soft-drink can.
-- Randy M. Dumse www.newmicros.com Caution: Object in mirror are more confused than they appear.
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I haven't handled the product, but the Lynx version looks like its final link (the gripper part itself) could be re-created so that its actual grip portion is wider, but that might reduce the closed size as well (which may not be an issue for you). The parallel linkages are the next item to consider replacing, or perhaps extending by epoxying onto them a piece of metal, perhaps 1/4"x1/16" x 3/4" long and with a hole in the end.... but this version may not look pretty.
Another random thought is to ask the makers to sell you a version that is scaled up by 50%. Some areas of it may not scale, such as the servo mounting holes, but the modifications to the design may be fairly quick for them to do. The cost for this custom order may be within your budget, and save you from having to machine your own parts.
Joe Dunfee
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At an industrial level, here's what you want:
    http://www.schunk-usa.com
Not cheap, though.
Here's a directory of industrial suppliers:
http://www.motionnet.com/cgi-bin/search.exe?a Êt&no2
                    John Nagle
D Herring wrote:

http://www.budgetrobotics.com/shop/?shop=1&cartF6428&cat5&noCookiePassThrough=Y&

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Just an idea ... JCD
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On Jul 22, 4:31 pm, snipped-for-privacy@keenebroadband.com wrote:

Can you please give an idea of "not very expensive"? Do you consider $1000 each expensive? Can you use a pneumatic type unit which are more common in industry? Here's a video of one that I designed that can be seen picking up a tray about half way through this video: http://smttech.com/shared_pics/PickAndPlaceLres.wmv
Pete B.
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